1. Field of the Invention
The present invention relates to a substrate processing apparatus and to a method of transferring the substrate to a processing chamber of the apparatus. More particularly, the present invention relates to a substrate transfer module for transferring a substrate from a container to a substrate processing chamber.
2. Description of the Related Art
The manufacturing of semiconductor devices generally includes a photolithographic process in which a photoresist pattern is formed on a wafer, and a dry etching process in which the wafer is subsequently etched using the photoresist pattern as an etching mask. The dry etching process is performed in a processing, chamber under a high vacuum state. However, a considerable amount of time is required for creating the high vacuum state in the processing chamber, i.e., for reducing the pressure from atmospheric pressure to a high vacuum pressure. Therefore, a low-vacuum loadlock chamber is used as a buffer in a dry etching apparatus so that wafers may stand ready while the high vacuum pressure is being created in the process chamber, whereby the wafers may be processed efficiently.
FIG. 1 is a plan view of a conventional multi-chamber dry etching apparatus for wafers having a diameter of 200 mm. Referring to FIG. 1, the conventional dry etching apparatus includes low-vacuum loadlock chambers 14a and 14b, a transfer chamber 15, and high-vacuum processing chambers 18a, 18b and 18c. 
A cassette 12 that accommodates about 25 wafers, that is, semiconductor substrates 20, is loaded into the loadlock chamber 14a. A low-vacuum state of about 10−3 Torr is maintained in the loadlock chamber 14a. Thereafter, the wafers 20 in the first loadlock chamber 14a are transferred one-by-one to respective processing chambers 18a, 18b and 18c using a robot 16 disposed in the transfer chamber 15. All of the processing chambers 18a, 18b and 18c are maintained at a high-vacuum state of about 10−6 Torr. The wafers 20 are also transferred by the robot 16 to the second loadlock chamber 14b after the dry etching process is completed within the processing chambers 18a, 18b and 18c. The wafer cassette 12 in the second loadlock chamber 14b removed from the dry etching apparatus once all of the etched wafers 20 are received in the cassette 12.
Meanwhile, larger wafers are now being used to improve the efficiency of the overall semiconductor device manufacturing process and to save manufacturing costs. In particular, semiconductor wafers having a diameter of 300 mm are now being used to manufacture semiconductor devices. Accordingly, the semiconductor manufacturing apparatus and processes have been developed in line with the increase in the size of the wafers being used.
For instance, wafers having a diameter of 300 mm are stored and transported within a wafer container such as a front opening unified pod (FOUP). The FOUP is has a relatively large volume. Therefore, when the FOUP is introduced into the low-vacuum loadlock chamber, a large amount of time is required to reduce the pressure in the loadlock chamber from atmospheric pressure to a low vacuum pressure. Likewise, a large amount of time is required to subsequently increase the pressure in the loadlock chamber from the low vacuum pressure to atmospheric pressure. Therefore, the efficiency of the dry etching process using this type of apparatus is relatively low.
More specifically, apparatus for processing 300 mm wafers include a separately formed substrate transferring module, such as an equipment front end module (EFEM). The FOUP is loaded on a load port of the substrate transferring module and the wafers are transferred one-by-one to the loadlock chamber via the substrate transferring module.
FIGS. 2 and 3 show a conventional multi-chamber dry etching apparatus for dry etching 300 mm wafers. Referring to FIG. 2, the conventional dry etching apparatus includes a substrate transferring module 50, low-vacuum loadlock chambers 60a and 60b and a substrate processing section 65. The substrate processing section 65 has a plurality of high-vacuum processing chambers 66a, 66b and 66c in which predetermined processes are carried out on the wafers 62, and a transfer chamber 63 through which the wafers 62 are transferred between the loadlock chambers 60a and 60b and the processing chambers 66a, 66b and 66c. 
As shown in FIG. 3, the substrate transferring module 50 includes load ports 58a and 58b for supporting FOUPs, a filter unit 59 for filtering air from the outside, and a substrate transfer chamber 54 in which a substrate transferring robot 56 is installed. Referring to FIGS. 2 and 3, the FOUP 52 accommodates one lot of wafers, e.g., 25 wafers 62. The FOUP 52 is placed on the first load port 58a of the substrate transferring module 50. Then, a front door (not shown) of the FOUP 52 facing the substrate transfer chamber 54 is opened.
The filter unit 59 of the substrate transferring module 50 is a fan filter unit (FFU) in which a fan and a filter are combined. The filter unit 59 allows the clean air 80 from a clean room filter 75 to flow down into the substrate transferring chamber 54. Accordingly, the substrate transferring chamber 54 has the same temperature and atmospheric pressure (temperature of about 23° C., humidity of about 45%) as the clean air 80 flowing from the filter unit 59. Since the FOUP 52 is connected to the substrate transfer chamber 54 while the front door of the FOUP 52 is opened, the clean air 80 flows from the substrate transfer chamber 54 into the FOUP 52. Hence, the interior of the FOUP is at the same temperature (room) and pressure (atmospheric) as the air in the substrate transfer chamber 54.
A first one of the wafers 62 is loaded into the first loadlock chamber 60a in which a low-vacuum state of about 10−3 Torr is maintained, using the substrate transferring robot 56 disposed within the substrate transfer chamber 54. Then, the wafer 62 in the first loadlock chamber 60a is transferred to a respective one of the processing chambers 66a, 66b and 66c by the transferring robot 64 disposed within the transfer chamber 63. A high vacuum pressure of about 10−6 Torr is maintained in all the processing chambers 66a, 66b and 66c. 
Once the first wafer 62 is dry etched, the wafer is transferred to the second loadlock chamber 60b using the transferring robot 64. After that, the first wafer 62 is transferred to a FOUP 52 disposed on the second load port 58b using the substrate transferring robot 56. The wafer remains there in the FOUP 52 for about 50 minutes until the remaining wafers are processed. When all of the other wafers are processed and received in the FOUP 52, the front door of the FOUP 52 is closed and the FOUP 52 is removed from the dry etching apparatus.
As described above, in the conventional dry etching apparatus for dry etching 200 mm wafers, a wafer cassette accommodating 25 wafers is directly loaded into the low-vacuum loadlock chamber so that the cassette is isolated from the external clean air. On the contrary, in the conventional dry etching apparatus for etching 300 mm wafers, the wafers are transferred to the first loadlock chamber 60a one-by-one from the FOUP 52 using the substrate transferring module 50. That is, the FOUP containing the wafers 62 remains on the second load port 58b of the substrate transferring module 50 while the front door of the FOUP 52 is opened and exposed to the clean air 80. Thus, the processing of the 300 mm wafers requires a great deal of time.
The characteristics of the conventional dry etching apparatus for etching 200 mm wafers and the conventional dry etching apparatus for etching 300 mm wafers are set out in the following Table 1.
TABLE 1123456789200cleanCassette intransferprocessingtransfercassette incleanmmroomloadlockchamberchamberchamberloadlockroomchamberchamber25 wafersby 1by 1by 125 wafers110−310−610−610−610−31atmTorrTorrTorrTorrTorratm300FOUPEFEMload-transferprocessingtransferloadlockEFEMFOUPmmlockchamberchamberchamber25by 1By 1by 1by 1by 1by 1by 125waferswafers1110−310−610−610−610−311atmatmTorrTorrTorrTorrTorratmatm
As shown in Table 1, in the conventional dry etching apparatus for etching 300 mm wafers, the wafers are under room temperature and under an atmospheric pressure as they are transferred one-by-one between the loadlock chamber and a FOUP connected to the substrate transferring module (EFEM). Therefore, a great deal of time elapses while the etched wafers remain in the FOUP while the front door of the FOUP is open.
During this time, these wafers standing by in the FOUP are exposed to the clean air via the substrate transferring module. Accordingly, the wafers in the FOUP are exposed to various airborne molecular contamination (AMC) such as moisture (H2O) and ozone (O3) in the clean air. In this case, etching gas remaining on the surface of the wafer and the moisture in the air react, i.e., the etching gas condenses. The condensed etching gas forms minute particles that may bridge adjacent conductive patterns on the wafer.
FIG. 4 is a graph illustrating the number of particles of condensed etching gas that form over time on a wafer after the wafer is dry etched. The delay time (hours and minutes) in the graph is the amount of time a wafer is exposed to the ambient, e.g., the clean air. In the graph of FIG. 4, the delay time is the time that elapses from the completion of the dry etching of the wafer to the time the FOUP storing the wafer is transferred to the inspection apparatus. FIG. 4 shows that the number of particles on the wafer increases dramatically after a delay time of about 100 minutes. Therefore, such long delay times allow for the contamination of the wafer to intensify. Moreover, the contamination is particularly deleterious when the pattern on the wafer is minute, i.e., has a small critical dimension. For instance, particles of ozone can facilitate the growth of a natural oxide layer and thereby increasing the resistance of the pattern, and moisture can cause a gate oxide layer to deteriorate.
These ‘condensation phenomena’ are most severe for the first wafer which remains within the FOUP for the longest time while at room temperature and under atmospheric pressure. The condensation phenomena also occur in the conventional dry etching apparatus for etching 200 mm wafers. However, those problems can be solved by managing the delay time after the wafers are tracked out from the dry etching apparatus up until the time the wafers are subjected to a subsequent cleaning process. In the conventional dry etching apparatus for etching 300 mm wafers, the first wafer experiences a delay time of about 50 minutes while the FOUP is connected to the substrate transfer module of the dry etching apparatus, i.e., a condensation phenomenon may occur before the wafer is tracked out.
A processing apparatus for dry etching 300 mm wafers, in which the FOUP is directly loaded into a low-vacuum loadlock chamber, has been developed in an attempt to reduce the contamination of the FOUP and the wafers therein. However, the loadlock chamber of this apparatus must have a large volume to accommodate the relatively large FOUP. Hence, a great deal of time is required for forming a vacuum in the loadlock chamber of this apparatus. Accordingly, the efficiency of the apparatus is rather low. Therefore, the above-described apparatus in which the wafers within the FOUP are transferred to the loadlock chamber one-by-one via a substrate transferring module is generally used to process 300 mm wafers.